Telephone system



' April 5, 1938. R. TAYLOR :7 AL 2,113,119

TELEPHONE SYSTEM Filed Jan. 15, 1936 4 SheetsSheet 1 April 1938. R. TAYLOR ET AL 2,113,119

' TELEPHONE SYSTEM V Filed Jan. 15, 193 4 snaps-Sheet 2 A ia/N410 721mm? 650 665 7791/45 54(6)? Irma 2 Apfil5,1938. R. TAYLOR ET AL I 2,113,119

TELEPHQNE SYSTEM Fil ed Jan. 15, 1936 4 Shets-Sheet 5 April 5, 1938. l R. TAYLQRI ET AL TELEPHONE SYSTEM Filed Jan. 15, 1936 4 Sheets-Sheet akoY :1

LINE

- LINE Pia/M410 Jar/0K 660(61" 72 0/4145 644 5?- Jrmmer oi'theba'nka' fl'atehted Apr. 5,1938

UNITED-"STATES.

TELEPHONE SYSTEM George Thomas Baker; assignors to Associated Reginald Taylor and Liverpool, England,

Telephone, & Telegraph Company, Chicago, Ill., a corporation of Delaware Application January 15,

In Great Britain February 4, 1935 p Claims. (0l. 179-18) 1 The present invention relates to telephone systems and is more particularly concerned with system employing final selector switches provided with two or more sets of wipers, the re- 5 quired set being connected up by the operation of one or more discriminating relays. The obloci; of the invention is to provide for more satis-i factory operation of such switches and for new trunking arrangements whereby their improved i'acilities may be used to better advantage.

According to one feature of the invention in an automatic switch provided with a plurality oi" sets of wipers determination of the set of wipers to be used is effected in accordance with route over which the switch has 5 been seized but only after the setting operation has commenced According to another feature of the invention in an automatic switch provided with a plurality of sets 01' wipers the determination of the set oi to be used is effected in the inter 4 digital pause between two trains of impulses transmitted for setting the switch.

A iurtha' feature oithe invention is that in a telephone system employing automatic switches with a phrality of sets of wipers wiper discrimination at the final selectors is eflected in accordance with the route over which the switch is seized, all the possible routes extending from the same position of a preceding switch over the.

same set of wipers. I

'Ihe invention will be better understood from the following description 0! one method oi-carrying it into eflect, reference being had to the accompanying drawings. These comprise Figs. 1

and 2 which show a 200-line 'fln'ai selector arranged ior ordinary operation and Figs. 3 and 4 which show a 200-line final selector adapted to perform a P. B. x. hunting operation on any level.

The mechanical construction of the switch to, which the circuits apply is assumedto be similar to that described inthe applicationv of R. N. saxby. Serial No. 634,285,- tiled 22nd September 4 1932, now Patent 2,028,689,;granted Jan. 21,

1938, in which only two magnets are provided for a vertical and rotary type switch and release is brought about by the further operation 0! the rotary magnet which advances the wipers clear Referring now to Figs. 1 and 2, it will first be assumed that the switch is taken into use over the odd set of conductors negative I. positive:

' i ind Pt'in' which case itsoperation does not involve the ener'giaation of the wiper switching pletes'a locking circuit for itself. armature hi direct earthis-connected to the'test 1930, Serial No. 594st relay. WS. when the speaking leads are l relay A operates and at armature al' brings up relayB which, guards the circuit by placing earth on the release trunk conductor at armature bl f and at armature 66 operates relay C. Upon the reception of the tens digit-relay A repeats the impulses through the low resistance. leitv-hand winding-of relay C to the vertical magnet ,VM

which according'ly'raises the wipers tothe desired levelu On'the first vertical step the of! normal springs are mechanically operated thereby at springs Ni short circuiting the right-hand winding of relay C which however, remains held during impulsinz over its other winding. It will be understood that the short-circuited winding or relay C*acts ,as a copper slug and the relay is thus made slow releasing. Relay B is also held during impulsing by the assistance 01' the copper sing on its core.

' At the end of the tens digit, relayA remains energized and relay C releases after a short in terval and at armature cll completes s circuit for operating relay E in series with the-vertical magnet VM. Relay, E at armature ei transfers the impulsing circuit to the-rotary magnet RM and at armature e2 removes the short circuitirom relay '0 which thereupon re-operates and transiers the holding circuit for relay E to the control oi its own armature .ei. The units digit when received is similarly repeated by relay A through the low resistance winding oi relay C tothe r0 tary magnet RM which advances the wipers into engagement withthe required subscriber's line.

On the first rotary step the rotary oi! normal springs are mechanically operated, thereby at springs NRI short circuiting the left-hand wind- I ing of relay C which again holds during impuls-- ing over its "other winding. I

At he'endoi the units digit, relay C releases and: opens the circuit of relay E-and during the slow release period-oi the latter a testing circuit is completed for relay H to the test wiper PI.

.11 the line is free, relay H operates in series-with the cut oi! relay oi the called subscriber's lihe" hi comcircuit and at the makeiirst armatge oreover.

wiper Pl to busy the called line and at armatures hi and M the ringing circuit is prepared. Up-

on the release of relay E aiter its slow periods circuit is completed over armature cl tor operat 1 in'g relay J which thereupon locks over its armature ii and at armatures 18 and i5 compietesthe' ringing circuit includingthe generator GNR, the

' left-hand winding of relay 1" and the-ringing re- C has re-operated and at armature cl preparesa circuit for re-operating relayE.

When the called subscriber replies, the direct current loop completed across the line causes the ring' trip relay F to energize whereupon byoperating its light armature Ii it locks up over its right-hand winding in series with relay H. Relay F cuts oil the ringing current at armatures f2 and f3 and completes the talking circuihbetween the calling and called parties. Relay D'now opcrates over the called subscriber's loop in series with the iron-hydrogen current limiting resistance BRA. This resistance has the property of limiting the current passing therethrough to a predetermined value and its purpose is to maintain a constant battery feed to the called side 'of the circuit over a wide range of loop resistances. Relay D at armatures di and d2 provides the usual supervision by reversing current to the calling side of the circuit and at armature dl oper-, .ates relay E which locks up at armature c8 and at armature e5 connects booster battery to the release trunk conductor to operate the calling subscribers meter in the well-known manner. Relay E also at armature e3 releases relay J the Irelease time of; which determines, the duration of application of the metering pulse after which earth lyre-connected to the release trunk conductor at the resting springs of armature 12 to guard the circuit. Relay J upon releasing opens the circuit of relay E which also releases after its slowwithout any material change to the circuit connections.f Clearly if relay D initially operates intermittently due to clumsy removal of thereceiver by -the-called party, relay E remains lockedand there will be no false interruption of the metering pulse.

If the called subscriber is busy, relay H will not operate owing to the absence of battery onthe test contact and upon the release of relay E a circuit is-completed over arrnaturee3 for operating relay G which at armature gl connects busy flash and tone from the cam assembly BT to the lower winding of relay A and at armature 02 connects the busy'hold cam assembly BE in circuit with the left-hand winding of relay'B in order that this relay shall be held. during the flash period when mam-. releases. 7

At the end of the conversation when the calling party replaces hisreceiver, relay K releases and allows relays B, C, F and H to fall away whereuponearth on the release alarin common I. provides a self-interrupted driving circuit for the rotary magnet RM to advance the wipers clear'of the bank so thatthey restore to the home position where the circuit is opened'by the ofi= normal springs N3. Relay B upon releasing, at armature bi removes the guarding earth from the release trunk conductor to enable the .preceding switches to restore butupon the release of relay C earth is re-applied to the releasetrunk conductor over armature. c3 until the switch 'arrives at its home position where the earth is disconnected by the off-normal springs N2. Under all conditions of release it is arranged that relay B'releases relay ,0 in'the manner described and therefore the unguard period on the release trunk conductor is determined by the releasing time of relay C which is substantiallyconstant. It should also be noted that seizure of the switch during the unguard period does not interfere with the release because the initial operating circuit of relay B is available only when the switch is in its normal position.

when the switch is taken into use overthe even set of conductors negativel, positivc 2, and P2,

the circuit operations are the same as described up to the end of the tens digit where relay E operates on the release of relay C. In these cir-,

cumstances the operation of armature e4 removes,

a short-circuit from the left-hand winding of the wiper switching relay WS and enables it to operate in series withthe line relay A. Relay WS locks over its other winding and armature 108i .and as .soon as the rotar movement of the switch begins. its operatin winding is again short-circuited by the normal rotary springsNRl.

This arrangement provides constant seizure time regardless of the route over which the switch is taken into use. Operation of the switch now' proceeds as described with the exception that the lower set of wipers are connected up to enable selection to take place in the even hundred group of lines. It will be noted that with relay WS' operated the conductor ll extending to a common timer is connected to' the test jack Tl so that if a link 'is inserted in the appropriate test jack springs the buzzer may be operated to indicate to an attendant when the lower set of ,wipers is in use. In the event of the test wiper Pi or P1 encountering booster battery from a line in the metering'condition there is no danger of false switching since the windings of relay H are arranged to neutralize as soon as the makefirst armature hJ closes and full operation of the relay is prevented,

The circuit includingarmatures d! and II and lamp LP extends by way of common conductor II to an alarm and serves to indicate if, the called subscriber is held unduly owing to the calling subscriber failing to hang up.

Referring now to the operation of the P. B. X.

. final selector switch slipwn in Figs. 3 and 4 it will be understood without further description that.

as regards the setting of the wipers and the selection of an ordinary line the operation of the circuit is the same asin Figs. 1 and 2.

gagement with the first line of aP. B. X; group, one or other of the group testing wipersPZ' will encounter battery since theP! contacts are wired as shown'in the lower corner of Fig. 4-, Come-- When the wipers of theswitch are set into enquently if. relay H fails to operate owing to the 'flrst line being busy, relay HS operates over its upper winding to prepare the switch for autmmatic rotation and at-armatu-re hsl switches one winding of relayG into the testlngcircuit of relay H. when relay E releases, relay C re-o r- 1 'ates and at armature ci in conjunctionwith armaturefisl completes a circuit'for the rotary on to the next set of contacts. At the end of the' magnet stroke the interrupter springs rm close and complete a circuitfor energizing relay G-over its lower winding so that this relay in turn at armature 95 opens'the circuit for the rotary magnet ,This interaction between the rotary magnet and relay 0 serves to rotate the wipers in search of a free line .in the P. B.' X. group. During hunting, relay, as. is intermittently edmagnet RM which energizes to advance the wipers ergi'zedby armature 04 but remains held with the assistance of its c pper sing and the shunt-v ing effect of the lower winding of relay H.

. When a free line is found; relay 1! operates in 17g series with'the called subscriber's cut-oi! relay and relay G which now holds to prevent further rotation of the wipers. Relay H then locks independently over its other winding and armature" hi, and at armature k2 connects direct earth to operating relay J which thereupon applies ringing current to the selected line.

When the called subscriber replies, the ringing is tripped and a booster battery pulse is applied to the release trunk conductor in the manner described in connection with Figs. 1 and 2,

to effect the operation of the calling subscriber's meter. The'metal rectifier MBA is provided to prevent relay G from operating if the Pl wiper should pass over busy lines in the metering condition.

It all the lines in the group are busy, the group testing wiperii32 encounters earth on the last contact whiclfholds relay G over its lower wind-:

I ing in series with resistance YO. Relay G opens the circuit of relay HS which releases alter its slow period and extends the busy flash and tone signal to the calling subscriber;

. In the event of the wipers oi! one switch passing oyer contacts engaged by the wipers of t another switch which has just been directively set to an intermediate linepthere is a possibility that the G relay of the hunting switch and the HS relay of the stationary switch will operate in series. To obviate this a high resistance YC is connected in circuit-with the lower winding of I relay G which definitely prevents relay HS from operating. Relay G however can operate but 1 only during the comparatively short slow release period of relay E in the stationary switch, and

accordingly there will be little'or no interruption to the hunting movement oithe first switch.

A switch of the kind above described is particswitchingstages not fully utilized are eliminated.

Thus it the switch isseized iroma 200-outlet group selector arranged to respond to a preliminary digit without aneiiective setting of its wipers, a 4000 line exchange can be provided with only two ranks of switches. The group selector would need to be of 800 points capacity with two sets of wipers each having access to 400 contacts and associated with a diflerent group of final selectors. The preliminary digit would deter-' mine which set of wipers was to be useifand hence which group of final selectors would handle the call and also which positive lead was toibe used so as to determine wiper selection in the final selector. The preliminary digit might operate a relay counting chain or a small auxiliary rotary switch or the main switch might be given a preliminary vertical setting and then drop back in readiness for resetting by the subsequent digit.

Alternatively of course, the final selector according to the. invention maybe arranged for seizure from two diflerent groups oi'group selectors or from diiferent levels oi the same group selector.

We claim: A

Is In combination, an automatic switch hava ing two sets 01 wipers, two routes over which said switch may be seized, means for directively operating said switch after seizure over either route, and meansefiective only ai'ter the switch has been operated for selecting one of said two sets of wipers in accordance with the route over whic seizure lo! the switch has been effected.

- 2. In combination, an automatic switch having two sets of wipers, two routes over which connections may be extended to said switch, mea in said switch responsive to primary and seco d'ary controlfexercised over the particular route used in extending connection to the switch for effecting the setting thereof, and means in said switch controlled in accordance with the route in use and during apause between the primary and secondary controlling operations ior effecting wiper selection.

-3'. In combinatioman automatic switch having two sets of wipers, wiper selecting means, two trunk conductors over which'a plurality of series of impulses may be transmitted to said switch to setthe same on a called line, said trunk con- Qductors being used/alternatively. depending on which set of wipers has access to the. called line, and means for controlling said selecting means during the spacing between two successive series of impulses and ,in accordance with the trunk conductor over which the. impulses are being transmitted. I

4. In combination, an automatic switch having two sets of wipers. a line relay in saldswitch, a circuit for said line relay including a talking conductor incoming to said switch, a wiper switching relay included in said circuit, said switching relay ularly suitableior inclusion in a system wherebybeing normally short circuited, setting means in said switch controlled by said line relay responsive to impulses transmitted over said circuit, and

- means eil'ective after impulses have been received for momentarily removing the short circuit from said switching relay to permit the same to energize in series with said line relay.

both said routes extendingirom the same position of the said selector wiper set and the route used being determined by which of said altema-' tive wipers is'used. and wiper selectingmeans in said connector controlled in accordance with the route over I the connector is seized.

' TAYLOR. 7

GEORGE THOMAS 

